In telephone systems pairs of twisted wires are enclosed in cables carrying many pairs of such wires. Each twisted pair is color-coded or otherwise coded to identify both ends of the same wire at each end of the cable. Long lengths of such cable are wound on spools for shipment and storage.
It is desirable to test each twisted pair of wires in a spool of cable before the spool is shipped to a customer. Testing not only is needed to find discontinuities in a wire but also to determine whether the electrical-carrying ability of the wire is interfered with by induction or other interference caused by adjacent wires. The wire pairs must be tested after manufacture of the cable is completed to ensure that defects caused by manufacture of the cable or the electrical characteristics of adjacent pairs of wires will be found before the cables are shipped to customers.
Present devices for testing cables of twisted pairs of wire require individually stripping wire ends or piercing insulation of each wire and connecting it electrically to a testing console that contains test elements for those electrical characteristics of the cable that are of interest. Some cables carry a few wires while others carry many--sometimes fifty pairs of wire, or more. Connecting wires to a console is time-consuming and during the time that the wires are being prepared for and connected to the testing console, the console cannot be used to test other cables. Presently-used testing devices also require elaborate switching means to bring the wires being tested in circuit with elements of the testing console. As a result, testing spools of cable is a time-consuming procedure that is sensitive to different electrical connections between the ends of the wires in the cable and the testing device. Also, the testing procedure requires multiple-switching means to bring each wire in circuit with the testing means, which introduces the different characteristics of the different switches into the testing circuit and which adds expense to the testing device and the procedure for using it.